GFS Upgrade Implementationscheduled August 22, 2006Scientific Decision Briefing

Mark Iredell

Global Climate and Weather Modeling Branch

August 18, 2006

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Goals of this GFS implementation

• Correct several user-specific problem areas (particularly stratospheric ozone, Antarctic ice, and snow analyses)

• Minimize impact to other GFS customers (negligible effect on hemispheric scores, precipitation, or tropical storms)

• Upgrade code infrastructure in the GFS

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GFS Implementation changes• Analysis changes

– None• Forcing changes

– Orography and land sea mask– Snow analysis processing– Land property quality control

• Physics changes– Ozone physics– Glacial ice– Longwave radiation at surface

• Dynamics changes– Time filter

• Infrastructure changes– Full ESMF compliance– Consolidated I/O

• Post processing and product changes– None

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Forcing changes

• New orography and land sea mask– Labels shelf ice as land not ocean– Uses upgraded Antarctic orography– Corrects other minor navigation errors

• Improved snow analysis processing– Removes double interpolation error– Particularly helps around the Alps

• Land property quality control– Guards against incompatible land states

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Physics changes

• Ozone physics– Uses algorithms contributed by NRL through JCSDA

and adapted by EMC– Removes low tropical bias in total ozone in GFS

• Glacial ice– Uses new land model algorithm dealing with polar

shelf ice

• Longwave radiation at surface– Corrects error in downward radiation at surface

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Dynamics changes

• Time filter– Increases amount of time filtering (coefficient

changed to 0.85 from 0.92)– Achieves greater stability without affecting

forecast

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Infrastructure changes

• Full ESMF compliance– Uses community software framework in operations– Enables GFS coupling; GFS is now enabled to couple

to itself in ensemble mode in the future

• Consolidated I/O– Common GFS I/O package among GFS programs– Enables full precision restart files, and future hybrid

sigma-pressure-isentropic and space environment versions of the GFS

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So what happened to the hybrid sigma-pressure GFS?

• The hybrid sigma-pressure GFS was just a little bit too expensive on the current CCS. EMC and NCO exerted heroic effort trying to speed it up and fit it, but the fit was just too close for comfort.

• Some sort of hybrid coordinate should be implemented early next year in the GFS with the GSI implementation.

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Testing set

• Retrospective testing– six 2005 tropical storms

(Dennis, Emily, Katrina, Ophelia, Rita, Wilma)– Summer 2005 (2 weeks)– Winter 2005-2006 (4 weeks)– Verification: http://www.emc.ncep.noaa.gov/

gc_wmb/wd20xw/

• Real-time parallel– EMC (hybrid version) since mid-May 2006– NCO (sigma version) since mid-July 2006

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Extratropical 500 Z AC (summer)

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Extratropical 500 Z AC (winter)

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Precipitation scores

Summer 12-36 hour (new in blue) Winter 12-36 hour (new in blue)

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AVERAGE TRACK ERRORS (NM) FOR HOMOGENEOUS SAMPLE

00 12 24 36 48 72 96 120 PRS 10.1 40.4 59.4 75.8 88.6 128.5 212.4 310.4 PRH 9.3 40.5 57.4 75.4 88.1 127.7 214.4 312.0 #CASES 46 44 41 38 35 29 24 18

AVERAGE ERRORS RELATIVE TO PRS (%)

00 12 24 36 48 72 96 120PRH -8.0 .2 -3.4 -.6 -.6 -.6 1.0 .5 #CASES 46 44 41 38 35 29 24 18

Hurricane Track Stats (Atlantic)Hurricane Track Stats (Atlantic)

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Operational Parallel

Total Ozone Forecast Errors(courtesy Craig Long – CPC)

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new Antarctic Ice Shelves(graphics from analyses valid 2006-08-15)

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Snow in Po valleyis unrealistic

Valley free of snow

Water equivalent in mm.

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NCEP Centers Review Summaries

• CPC, HPC, AWC, and TPC all reviewed the GFS changes and all recommended implementation

• The details of the centers’ responses will be briefed by NCO